The present invention relates to oil pans for reciprocating internal combustion engines, and, more in particular to an oil pan having a skimmer to reduce friction loss from oil contacting rotating parts of the engine.
Internal combustion engines use oil pans to collect and store oil as a source of oil for an oil pump that distributes it under pressure throughout the engine. The pans may be wet sump or dry sump, the former storing a larger volume of oil than the latter. The rotating parts of the engine, especially the crankshaft and connecting rod bearing caps, get excess oil on them. Centrifugal force throws this oil from the parts. The thrown oil, being uncontrolled, will cause splash from contact with the oil pan and oil already in the collection volume of the oil pan. The splashing oil thrown against the rotating crankshaft and rod assembly produces drag on the rotating assembly by this impact. The wind created by the rotating crank and rod assembly creates additional splash by contacting the oil in the collection volume of the oil pan. This additional splash also creates drag on the crank and rod assembly by impact. The loss associated with wind related splash is known as "windage loss" while that of thrown oil is referred to as "oil impact loss."0 The consequence of too much oil on rotating parts is more than mere friction. Oil on the rotating parts has a mass which must be accelerated during engine acceleration that reduces the acceleration.
While some splash may be desirable in a typical engine's lubrication, the uncontrolled splash is considerably in excess of that necessary for lubrication.
Oil impact loss has been reduced with oil pans equipped with a skimmer. In wet sump pans, windage loss has been reduced by a windage tray. The skimmer is located very close to the rotating parts and scrapes oil from the rotating parts and directs it into a side pouch for collection in the oil collection volume of the pan. The windage tray underlies the rotating parts of the engine and creates a barrier between these parts and the oil collection volume of the pan.
For best performance the skimmer should be spaced from proximate crankshaft counterweights and connecting rod bearing caps and cap fasteners by between about 0.03 inch to about 0.06 inch (0.076 centimeter to 0.152 centimeter). This requires adjustment of the spacing, typically by grinding.
Different engines have different geometries, even when the engines are from the same manufacturer and are of the same model; differences in geometry can result from differences in the radius of crankshaft counterweights and length of stroke.
Previous skimmer equipped oil pans have had the skimmer integral with the pans. The adjustment required to produce the desired spacing between the rotating parts required for installing the pan on the engine. The pan prevented seeing the spacing between the scraper and the rotating parts, and adjustment was done blind. The desired spacing between the skimmer and the rotating parts was often lacking. The length of time for fitting was typically great unless a fortuitous fitting occurred early.